The deal will allow the transit agency to sign an $886 million contract Friday for 428 new rail cars, a high-priority purchase that was in danger of falling through. The federal government has agreed to give Metro $1.5 billion for capital needs over 10 years as long as Virginia, Maryland and the District match the money.

"These cars are extremely important to the safety of our customers," interim General Manager Richard Sarles said after the board drew up a contract with Virginia officials.

Of the 428 cars, 128 will help Metro provide service on the Silver Line extension to Dulles International Airport, and 300 will replace Metro's oldest rail cars.

The administration of Gov. Robert F. McDonnell (R) had threatened to withhold Virginia's share of the money unless the state gets two members on the Metro board. Four seats are held by elected officials from Fairfax and Arlington counties and Alexandria, and McDonnell wants to appoint two of them. Transportation Secretary Sean T. Connaughton said Virginia wants more accountability from Metro in the aftermath of last year's fatal Red Line crash. Including its contribution to the matching funds, the state will contribute more to Metro than the Northern Virginia local governments, Connaughton said.

But the state decided last week to pay without an agreement on the seats.

Late Thursday, Virginia officials signed the deal.

Thursday's agreement calls for Virginia to pay $50 million a year through fiscal 2016. Virginia's share would go through that year to match the timeline of the state's road program. Metro officials said they expect a successor deal. The District and Maryland have passed legislation that binds them to set aside their share.

Connaughton said he is negotiating with the Northern Virginia Transportation Commission, which appoints Metro board members nominated by the local jurisdictions, to give up two seats. But Thursday night, the transportation commission voted largely along party lines to defer until September a decision on whether Virginia should get representation on the Metro board.

Under the plan for the matching funds, the federal government appoints two principal members and two alternates to Metro's board. The Obama administration named two appointees in January, but the federal government has to fill two positions.

"We are simply asking for the same level of representation already given to the federal government, the state of Maryland and the District of Columbia," Connaughton said last week.

The first $12.5 million of Virginia's $50 million share was due Thursday. Johnson said that if the state signs the contract, it will make the first payment Friday. Connaughton's staff said last month that it did not plan to pay it unless the Northern Virginia commission met its demands. Commission officials pushed back, saying that the McDonnell administration was wrong to tie its commitment to help pay for safety upgrades with frustration over how the transit agency is governed.